As Ariel Sharon, the Israeli Prime Minister, began his visit to the United States yesterday to promote himself as a peace-maker, UN officials were totting up the cost of repairing the damage caused to residential areas, infrastructure and Palestinian institutions during the Israeli army's invasion of towns in the West Bank.

Damage to property is estimated at $300m to $400m (£200m to £270m), and repairs will take up to 18 months, Tim Rothermel, of the UN Development Programme in the West Bank and Gaza Strip, said.

The Israeli assault, launched after a blitz of suicide bombings, won huge support from Israelis – one poll found that 90 per cent of Israeli Jews approved – despite growing evidence that the Israeli army ran amok, and not only in Jenin refugee camp, where extensive atrocities have been documented.

Israel's Ha'aretz newspaper published a long account yesterday of the devastation, vandalism and looting wreaked by the Israeli army in the Palestinian Authority's Ministry of Culture in Ramallah, a building which was occupied by troops for about one month.

"In every room, books, disks, and documents were piled up, soiled with urine and excrement," wrote a correspondent, Amira Hass. "There are two toilets on every floor but the soldiers urinated and defecated everywhere else in the building ... Someone even managed to defecate into a photocopier."

The Israeli army said it had no specific comment, but insisted it took cases of vandalism or wanton destruction "very seriously".

UN, World Bank and EU officials are expected to complete an assessment of damage in a week, and draw up a reconstruction plan which will be distributed to donor countries.

The Israeli armed forces shed new light yesterday on how one of its tank crews managed to shoot dead a Palestinian woman and two of her children, aged four and six, on Sunday. Its spokesman expressed regret for killing civilians, but initially said that the tank opened fire when a mine blew up near by. After no sign of an explosion was found, this story was amended. The new version was that the crew fired after receiving a scare from the "exploding sound" of one of the tank's treads coming loose.

The deaths received scant attention compared to saturation media coverage of the final throes of the 35-day siege of the Church of the Nativity in Bethlehem, where at least 132 Palestinians are holed up, surrounded by Israeli tanks and troops. After another day of negotiations – which now include the CIA's station chief in Tel Aviv, and officials from the Vatican, Britain and the EU – a deal appeared to be emerging.

Both sides have accepted that those inside the church – who include Christian clerics, Palestinian civilians, security officials, militiamen and European "peaceniks" – fall into three groups, but differ over numbers. The first group – regarded by Israel as wanted militants – is to be deported to Italy, and barred from returning to the occupied Palestinian territories. Palestinian negotiators have been pressing to restrict their numbers to six; Israel has been calling for between 12 and 20. The second group, of up to 40 Palestinians, would be removed to the Gaza Strip. And the third would be free to leave.

The intensity has been increasing as Mr Sharon's meeting with President Bush – later today – approaches. The Israelis are keen to have the matter wrapped up beforehand – a fact which is unlikely to have escaped the Palestiniannegotiators, pushing the deal-making to the wire. But they also know that if the meeting takes place and the siege is unresolved the Israeli terms could harden.